A sound source is moving towards a stationary observer with ( 1 10 )^ th the speed of sound, The ratio of apparent to real frequency is

Step-by-step solution

The Doppler effect governs the apparent frequency when a sound source moves toward a stationary observer. For a source moving toward an observer at rest, the apparent frequency is f′ = f ( v v - v_s ) , where v is the speed of sound and v_s is the source speed. Given v_s = v 10 , the ratio is f′ f = v v - v 10 = v 9v 10 = 10 9 . This matches option A .